This invention generally relates to systems and methods for detecting and correcting image quality defects generated by a rendering device, or printer.
Detection, and the subsequent correction, of image quality defects ensures the production of quality images by image rendering devices. There are various existing approaches for detecting image quality defects in images rendered by image rendering devices. For example, U.S. Pat. No. 6,377,758 by Ou Yang, et al., entitled METHOD AND SYSTEM FOR ANALYZING IMAGING PROBLEMS filed Apr. 23, 2002, describes a method and a system for analyzing imaging problems by printing an image, scanning the printed image and comparing the scanned image and the original image on a pixel by pixel basis to detect defects generated by an intermediate imaging member.
Further, U.S. Patent Application Publication No. 20060077489 by Zhang, et al., entitled UNIFORMITY COMPENSATION IN HALFTONED IMAGES filed Aug. 20, 2004, describes the use of sets of colorant-specific, spatially dependent compensating tone reproduction curves (TRCs) over temporal and spatial spaces of desired uniformity that extend across multiple rendering devices or print engines.
U.S. Patent Application Publication No. 20060110009, by Victor Klassen and Stephen Morgana, entitled SYSTEMS AND METHODS FOR DETECTING IMAGE QUALITY DEFECTS filed Nov. 22, 2004, the disclosure of which is totally incorporated herein by reference, describes an approach that includes identifying regions of interest (ROI) within a printed image that may be used to identify image quality defects. At each ROI, original image data may be compared to captured image data of a corresponding region to determine a color difference of the captured image. The color difference may be subsequently converted from a device independent color space to a device dependent color space. Based on the converted color difference and input intensity of the original image data, a colorant error correction may be determined and/or a scan line and a row line for that particular ROI.
The above approaches can provide substantial improvements in image quality and image consistency; however, they do not compensate for colorant appearance effects that are correlated to colorant interactions. For example, in offset printing, the efficiency with which an ink is absorbed or trapped can be influenced by the presence of another ink laid down earlier. Additionally, trapping efficiency is a function of transfer roller pressures. Spatial variations in those pressures may cause spatial variation in interacting colorant appearance. Related colorant appearance variations associated with print-head-to-print-media pacing variations associated with inkjet technology are also anticipated. In electrophotographic processes, spatial variations, due to, for example, manufacturing tolerances, wear, dirt and component age may produce spatially dependent charge, development field, cleaning field, toner concentration, raster output, raster output power, and/or roller pressure variations which may manifest as spatially dependent colorant appearance nonuniformities or variations. Some component or portion of these colorant appearance variations or nonuniformities may be correlated to interactions between colorants.